CALCIUM-DEPENDENT ACTION POTENTIALS PRODUCED BY CATECHOLAMINES IN GUINEA PIG ATRIAL MUSCLE FIBERS DEPOLARIZED BY POTASSIUM
CALCIUM-DEPENDENT ACTION POTENTIALS PRODUCED BY CATECHOLAMINES IN GUINEA PIG ATRIAL MUSCLE FIBERS DEPOLARIZED BY POTASSIUM
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DOI：
10.1161/01.res.27.3.379
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发表时间：
1970-01-01
影响因子：
20.1
通讯作者：
PAPPANO, AJ
中科院分区：
文献类型：
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作者：
PAPPANO, AJ
豚鼠的心房肌纤维被去极化，[K+]升高到22 mM时变得不可兴奋。异丙肾上腺素、肾上腺素和去甲肾上腺素恢复了心房细胞的传播动作电位和收缩，而不改变静息电位。细胞内记录的动作电位峰值变化28 mv，[Ca ~（2+）]o变化10倍。异丙肾上腺素诱导的动作电位恢复对大浓度的河豚毒素（3 × 10- 6 M）不敏感，但被Mn 2+（0.2 mM）拮抗。这些数据支持的建议，儿茶酚胺恢复兴奋性增加膜电导Ca 2+。除了儿茶酚胺，二价阳离子Ba 2+，Sr 2+和Ca 2+恢复动作电位心房肌纤维去极化升高K+。二价离子在允许动作电位中的有效性与估计的水合离子半径成反比。像在异丙肾上腺素的存在下观察到的动作电位，那些允许由Ba 2+，Sr 2+，和Ca 2+阻止Mn 2+，但不敏感的河豚毒素封锁。
Atrial muscle fibers of the guinea pig were depolarized and rendered inexcitable by elevation of [K+]oto 22 mM. Isoproterenol, epinephrine, and norepinephrine restored propagated action potentials and contractions to atrial cells without changing the resting potential. The peak value of the intracellularly recorded action potentials varied 28 mv for a 10-fold change in [Ca2+]o. Isoproterenol-induced restoration of action potentials was insensitive to large concentrations of tetrodotoxin (3 x 10-6M) but antagonized by Mn2+(0.2 mM). These data supported the proposal that the catecholamines restored excitability by increasing membrane conductance to Ca2+. In addition to the catecholamines, the divalent cations Ba2+, Sr2+, and Ca2+restored action potentials to atrial muscle fibers depolarized by elevated K+. The effectiveness of the divalent ions in allowing action potentials was inversely related to the estimated hydrated ionic radii. Like the action potentials observed in the presence of isoproterenol, those permitted by Ba2+, Sr2+, and Ca2+were prevented by Mn2+but insensitive to blockade by tetrodotoxin.